U.S. patent number 7,658,172 [Application Number 11/978,576] was granted by the patent office on 2010-02-09 for valve unit of internal combustion engine.
This patent grant is currently assigned to Mitsubishi Jidosha Kogyo Kabushiki Kaisha. Invention is credited to Masashi Igarashi, Shinichi Murata, Mikio Tanabe, Hitoshi Toda.
United States Patent |
7,658,172 |
Tanabe , et al. |
February 9, 2010 |
Valve unit of internal combustion engine
Abstract
A valve unit of an internal combustion engine is accommodated in
a space between a cylinder head and a rocker cover. The valve unit
comprises a camshaft, a variable valve operating mechanism, a
sensor, and a retaining member. The camshaft is provided with a cam
for each cylinder. The variable valve operating mechanism receives
a displacement of the cam, outputs a valve drive output, and
continuously variable-controls the valve drive output in accordance
with a rotational displacement of a control shaft provided
substantially in parallel with the camshaft. The sensor detects the
rotational displacement of the control shaft. The retaining member
retains the camshaft, the variable valve operating mechanism, and
the sensor. The retaining member expose the sensor to the out side
of the rocker cover thereby to fix the camshaft, the variable valve
operating mechanism, and the sensor to the cylinder head.
Inventors: |
Tanabe; Mikio (Obu,
JP), Murata; Shinichi (Okazaki, JP), Toda;
Hitoshi (Okazaki, JP), Igarashi; Masashi
(Okazaki, JP) |
Assignee: |
Mitsubishi Jidosha Kogyo Kabushiki
Kaisha (Tokyo, JP)
|
Family
ID: |
39144311 |
Appl.
No.: |
11/978,576 |
Filed: |
October 30, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080098970 A1 |
May 1, 2008 |
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Foreign Application Priority Data
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Oct 31, 2006 [JP] |
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2006-297044 |
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Current U.S.
Class: |
123/90.16;
123/90.44 |
Current CPC
Class: |
F01L
13/0063 (20130101); F01L 2001/0535 (20130101); F01L
2820/032 (20130101); F01L 2013/0068 (20130101) |
Current International
Class: |
F01L
1/34 (20060101) |
Field of
Search: |
;123/90.15,90.16,90.17,90.18,90.39,90.44,90.27,90.31
;74/559,567,569 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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20317384 |
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Feb 2004 |
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DE |
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1548240 |
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Jun 2005 |
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EP |
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1707765 |
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Oct 2006 |
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EP |
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1710402 |
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Oct 2006 |
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EP |
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11-81942 |
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Mar 1998 |
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JP |
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11-210434 |
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Aug 1999 |
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JP |
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2001-107713 |
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Apr 2001 |
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JP |
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2003-027973 |
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Jan 2003 |
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JP |
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2005-273507 |
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Oct 2005 |
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JP |
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2005-299536 |
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Oct 2005 |
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JP |
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2005-299538 |
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Oct 2005 |
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JP |
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2005-315183 |
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Nov 2005 |
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JP |
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Primary Examiner: Chang; Ching
Attorney, Agent or Firm: Birch, Stewart, Kolasch &
Birch, LLP
Claims
What is claimed is:
1. A valve unit of an internal combustion engine, which is
accommodated in a space between a cylinder head of the internal
combustion engine and a rocker cover of the internal combustion
engine, comprising a camshaft provided with a cam for each
cylinder; a variable valve operating mechanism for receiving a
displacement of the cam, outputting a valve drive output, and
continuously variable-controlling the valve drive output in
accordance with a rotational displacement of a control shaft
provided substantially in parallel with the camshaft; a sensor for
detecting the rotational displacement of the control shaft; and a
retaining member for retaining the camshaft, the variable valve
operating mechanism, and the sensor, and exposing the sensor to the
outside of the rocker cover thereby to fix the camshaft, the
variable valve operating mechanism, and the sensor to the cylinder
head, wherein the sensor for detecting the rotational displacement
is arranged at an axial end of the control shaft, and the other end
of the control shaft is coupled to an actuator mechanism for
rotationally displacing the control shaft.
2. The valve unit of an internal combustion engine according to
claim 1, wherein the variable valve operating mechanism comprises
an adjustment mechanism capable of adjusting the valve drive output
for each cylinder.
3. The valve unit of an internal combustion engine according to
claim 1, wherein the retaining member comprises a holder member for
holding one side of the camshaft in the diametric direction, the
variable valve operating mechanism, and the sensor, a cap member
for holding remaining one side of the camshaft, and a fixing bolt
member which penetrate the holder member and the cap member, and
can be screwed into the cylinder head.
4. The valve unit of an internal combustion engine according to
claim 1, wherein the plurality of retaining members are provided so
as to axis-support at least both ends of the camshaft and the
control shaft, and the retaining members are connected to each
other by the camshaft and the control shaft.
5. The valve unit of an internal combustion engine according to
claim 3, wherein the plurality of retaining members are provided so
as to axis-support at least both ends of the camshaft and the
control shaft, and the retaining members are connected to each
other by the camshaft and the control shaft.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority
from prior Japanese Patent Application No. 2006-297044, filed Oct.
31, 2006, the entire contents of which are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a valve unit of an internal
combustion engine in which a valve characteristic of an intake
valve or an exhaust valve is continuously controlled.
2. Description of the Related Art
In a valve unit of a multicylinder reciprocating engine (internal
combustion engine) mounted on an automobile, in order to reduce
fuel consumption by exhaust gas measures or by improving pumping
loss, a variable valve in which a characteristic of an intake valve
(or an exhaust valve) is continuously and variably controlled is
incorporated in a head part of a cylinder head covered with a
rocker cover.
In most variable valve units, a structure is used in which a
characteristic of an intake valve, e.g., an opening/closing timing
or a valve lift amount is continuously varied by a rotational
displacement of a control shaft received from a cam. A variable
valve unit of this type is disclosed in Jpn. Pat. Appln. KOKAI
Publication No. 2005-299536.
In most methods of installing such a variable valve unit, a method
is used in which, a cylinder head is mounted on a cylinder block on
a main line for assembling engines, and each part of the variable
valve unit is attached to each corresponding section of the
cylinder head, thereby assembling the entire variable valve
unit.
In recent times, in order to increase production efficiency of the
main line, on the main line, work in which only camshafts and
valves are attached to a cylinder head is performed. On a sub-line
separate from the main line, a method is used in which a variable
valve unit constituting a part of a cylinder head from a camshaft
to a valve is modularized.
That is, only the variable valve unit, which is troublesome in
assembly, is modularized on the sub-line, the modularized variable
valve unit is returned to the main line, and the variable valve
unit is attached to a cylinder head (which is already equipped with
camshafts and valves). By doing so, a measure is used in which a
working process taking much time is reduced on the main line.
Assembling methods of such a type are disclosed in Jpn. Pat. Appln.
KOKAI Publication No. 2005-299536 and Jpn. Pat. Appln. KOKAI
Publication No. 2005-299538.
Incidentally, the variable valve unit is required to continuously
control valves of cylinders in accordance with the same valve
characteristic so that a set performance can be exhibited in any
operational state of an engine. For that purpose, the variable
valve unit is required to undergo adjustment work for adjusting a
valve drive output in accordance with a cam profile of each cam for
each cylinder, thereby eliminating variation between cylinders.
However, in the above adjustment for eliminating variation between
cylinders, troublesome and considerably time-consuming fine
adjustment work for making relationships between cams and parts of
the variable valve unit for receiving the cams with respect to the
respective cylinders so that the continuously variable valve
characteristic can be appropriately exhibited is required.
Particularly, in the technique disclosed in Jpn. Pat. Appln. KOKAI
Publication No. 2005-299536, a contrivance is employed in which an
adjustment mechanism is incorporated in the variable valve unit,
the adjustment mechanism having a structure in which a position of
a part for receiving a cam is made adjustable, thereby facilitating
the adjustment work. For this reason, the adjustment work can be
performed only after the variable valve unit provided with parts
for receiving cams of a camshaft is attached to the cylinder head
provided with camshafts. Therefore, on the main line for assembling
engines, considerably time-consuming adjustment work (adjustment
for eliminating variation between cylinders) is still required,
which is a factor for causing stagnation of the main line.
Furthermore, in the adjustment for eliminating variation between
cylinders, not only simply making positional relationships between
cams and parts for receiving the cams uniform, but also making
uniform the valve characteristics on the basis of the continuously
variable control shaft is needed. Accordingly, work for attaching a
sensor for detecting a rotational displacement of the control
shaft, and work for adjusting the sensor is required on the main
line. Such work is also a factor causing stagnation of the main
line. Particularly, the sensor is an important part for
continuously and variably controlling the valve characteristic.
Therefore, the attaching of the sensor must be performed in
consideration of maintenance because maintenance of the sensor is
required in a state where the assembly of the engine is finished or
after the engine is completed as a product. Considering these
requirements, considerably difficult problems must be solved to
eliminate the stagnation of the main line.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a valve unit of an
internal combustion engine that can improve the productivity of the
internal combustion engine.
The valve unit of the present invention comprises: a camshaft
provided with a cam for each cylinder; a variable valve operating
mechanism for receiving a displacement of the cam, outputting a
valve drive output, and continuously variable-controlling the valve
drive output in accordance with a rotational displacement of a
control shaft provided substantially in parallel with the camshaft;
a sensor for detecting the rotational displacement of the control
shaft; and a retaining member for retaining the camshaft, the
variable valve operating mechanism, and the sensor, wherein the
sensor is exposed to the outside of the rocker cover, thereby
fixing the camshaft, the variable valve operating mechanism, and
the sensor to the cylinder head through the retaining member.
That is, in the valve unit, the camshaft and the sensor are also
combined with the valve unit, and hence the valve unit becomes a
structure in which cylinder-to-cylinder variation can be adjusted
singly. In other words, unlike the conventional case, it is
possible not only to complete the assembly of the valve unit on a
line separate from the line for assembling internal combustion
engines but also to perform adjustment of cylinder-to-cylinder
variation, e.g., adjustment of cylinder-to-cylinder variation using
a simulation system in which a cylinder head of an internal
combustion engine is simulated. Accordingly, the work required on
the main line is only work for attaching a valve unit, for which
adjustment has already been finished, to a cylinder head on the
main line. The cylinder-to-cylinder variation adjustment work and
the troublesome work for attaching the sensor and adjusting the
sensor, which become factors causing stagnation on the main line,
are made unnecessary. Furthermore, the sensor is attached to the
cylinder head in a state where it is arranged outside the rocker
cover, and hence maintenance thereof can be facilitated.
In a desirable aspect of the present invention, a configuration
including an adjustment mechanism capable of adjusting the valve
drive output for each cylinder is employed in the variable valve
operating mechanism.
In another desirable aspect of the present invention, the
configuration is made such that a sensor for detecting the
rotational displacement is arranged at an axial end of the control
shaft, and the other end of the control shaft is coupled to an
actuator mechanism for rotationally displacing the control
shaft.
In another desirable aspect of the present invention, the retaining
member comprises a holder member for holding one side of the
camshaft in the diametric direction, the variable valve operating
mechanism, and the sensor, a cap member for holding remaining one
side of the camshaft, and a fixing bolt member which penetrate the
holder member and the cap member, and can be screwed into the
cylinder head.
In a further desirable aspect of the present invention, the
Plurality of retaining members are provided so as to axis-support
at least both ends of the camshaft and the control shaft, and the
retaining members are connected to each other by the camshaft and
the control shaft.
Additional objects and advantages of the invention will be set
forth in the description which follows, and in part will be obvious
from the description, or may be learned by practice of the
invention. The objects and advantages of the invention may be
realized and obtained by means of the instrumentalities and
combinations particularly pointed out hereinafter.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
The accompanying drawings, which are incorporated in and constitute
a part of the specification, illustrate embodiments of the
invention, and together with the general description given above
and the detailed description of the embodiments given below, serve
to explain the principles of the invention.
FIG. 1 is a partial cutaway perspective view showing a cylinder
head of an internal combustion engine according to an embodiment of
the present invention together with a valve unit mounted on the
cylinder head.
FIG. 2 is an exploded perspective view showing the modularized
variable valve unit together with peripheral units and devices.
FIG. 3 is an exploded perspective view for explaining structures of
parts of the variable valve unit.
FIG. 4 is a cross-sectional view around a sensor taken along a line
indicated by an arrow A in FIG. 1.
FIG. 5 is a cross-sectional view around the cylinder head taken
along line B indicated by an arrow B in FIG. 1.
FIG. 6 is a cross-sectional view around the cylinder head taken
along line C indicated by an arrow B in FIG. 1.
FIG. 7 is a cross-sectional view taken along line D-D in FIG.
2.
FIG. 8 is a cross-sectional view showing an engine equipped with a
valve unit of an internal combustion engine according to a second
embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
A variable valve unit of an internal combustion engine according to
a first embodiment of the present invention will be described below
with reference to FIGS. 1 to 7. FIG. 1 shows a perspective view of
a head part of an engine main body in a reciprocating inline
four-cylinder petrol engine, which is an example of a multicylinder
internal combustion engine. FIG. 2 is a perspective view showing a
state where the head part is disassembled. FIGS. 4 to 7 are
cross-sectional views respectively showing states where respective
parts (cross sections taken along lines A, B, and-C in FIG. 1, and
line D-D in FIG. 2) are cross-sectioned.
A reference numeral 1 in FIG. 1 denotes a cylinder head mounted on
a head part of a cylinder block 2 (shown in only FIG. 5 by two-dot
chain lines). A reference numeral 3 denotes a rocker cover covering
an upper part of the cylinder head 1. A reference numeral 4 denotes
SOHC type variable valve unit which is in a space between the
cylinder head 2 and the rocker cover 3. The variable valve unit 4
is an example of a valve unit of the present invention.
The cylinder head 1 is provided with a head main body 1x. As shown
in FIGS. 1, 2, and 5, the head main body 1x is surrounded by a
peripheral wall 1a at an upper part thereof. A top surface 1y of
the head main body 1x is made lower than a rocker cover attaching
seat 1b formed at an upper end part of the peripheral wall 1a as
shown in FIGS. 5 and 6.
Combustion chambers 7 (shown in only FIG. 5) are formed on an
undersurface of the head main body 1x so as to correspond to four
cylinders 6 (shown by two-dot chain lines in only FIG. 5) formed in
the cylinder block 2. A pair of intake ports 8 and a pair of
exhaust ports 9 (both of which are shown in a part of FIG. 5) which
extend from the combustion chamber 7 are formed on both sides (in
the width direction) of the head main body 1x.
To the intake ports 8 of these ports, a pair of normally-closed
intake valves 8a are attached. A pair of normally-closed exhaust
valves 9a are attached to the exhaust ports 9. Stem ends of the
valves 8a and 9a protrude upwardly from the top surface 1y of the
head main body 1x. Incidentally, for example, an ignition plug is
attached to each combustion chamber 7, and an injector is attached
to each cylinder (both are not shown).
In the variable valve unit 4, a modularized structure in which
various parts are assembled is employed. To specifically describe
the modularization, as shown in, for example, FIGS. 2 and 5, a
variable valve operating mechanism 13 of the intake side having an
adjusting function, a control shaft 14 (serving also as a rocker
shaft for intake) for controlling the variable valve operating
mechanism 13, a camshaft 15, a shaft displacement detection sensor
16 (corresponding to the sensor of the present application) for
detecting a rotational displacement of the control shaft 14, and a
rocker arm mechanism 17 (only a part thereof is shown in FIG. 5) of
the exhaust side are assembled by using a plurality of (five)
retaining members 11a to 11c (only three representative ones are
shown).
Structures of respective parts will be described below. The
retaining members 11a to 11c are, as shown in FIGS. 1 and 2, parts
each having a wall-shape divided in accordance with an arrangement
of each of the cylinders 6 (four), and arranged at the foremost
part of the cylinder array, between the cylinders, and at the
backmost part in parallel with each other. Incidentally, the
retaining members may be only the foremost and backmost members in
the case of modularization. However, it is desirable that the
retaining member be provided between the cylinders in consideration
of the rigidity and the like.
As shown in FIG. 3, a two-piece structure provided with a
wall-shaped holder member 18a extending in the width direction
(direction perpendicular to the cylinder array direction) of the
cylinder head 1, and a cap member 18b to be combined with the
holder member 18a at a lower end part thereof, and a structure in
which a holder member 18a, a cap member 18b, and a plurality of
fixing bolt members 18c to be attached to the members 18a and 18b
so as to penetrate the members 18a and 18b are combined with each
other are used for these retaining members 11a to 11c.
Of the above members, each of the holder members 18a has the same
structure, and as shown in FIG. 3, an intake rocker shaft retaining
hole 20a and an exhaust rocker shaft retaining hole 20b arranged in
the lateral direction with a predetermined interval between them
are formed in the middle stage on both sides of each holder member
18a. On a top surface of the holder member 18a, an arcuate
attaching seat 21 is formed at a position between the intake rocker
shaft retaining hole 20a and the exhaust rocker shaft retaining
hole 20b and closer to the hole 20b. On an undersurface of the
holder member 18a, a semicircular journal bearing surface 22 is
formed at a position between the intake rocker shaft retaining hole
20a and the exhaust rocker shaft retaining hole 20b and closer to
the hole 20b. The entire undersurface of the holder member 18a
except for the bearing surface 22 is used as a cap attaching seat
23.
For example, a plate-like member having an arcuate recession at a
central part thereof is used as the cap member 18b. A semicircular
journal bearing surface 25 is formed at the central part on a top
surface of the cap member 18b, and the entire top surface except
for the bearing surface 25 is used as a cap attaching surface 26.
Incidentally, flat undersurface parts on both sides on the
undersurface of the cap member 18b between which the journal
bearing surface 25 is interposed are used as a module installation
seat surface 27.
Each of the foremost holder member 18a and cap member 18b has,
unlike the other members, a pair of leg parts 29 formed so as to
externally extend on both sides thereof. A journal bearing surface
22, a cap attaching seat 23, a journal bearing surface 25, a
cap-attaching surface 26, and a seat surface 27 are also formed on
the pairs of the leg parts 29.
Incidentally, through holes 28 in which head bolts (not shown) are
inserted are formed in the leg parts 29. A sensor attaching part 30
is formed on the holder member 18a arranged at the backmost
position. In the sensor attaching part 30, as shown in FIGS. 3 and
4, a structure in which a cylinder part 31a extending from the
intake rocker shaft retaining hole 20a toward the backmost position
is formed, and a fan-shaped sensor attaching boss 31b is formed at
a distal end of the cylinder part 31a is employed.
In the respective intake rocker shaft retaining holes 20a, as shown
in FIGS. 2 and 3, a control shaft 14 (constituted of a hollow
member) serving also as the intake side rocker shaft is rotatably
inserted so as to allow the shaft 14 to extend from the foremost
retaining member 11a to the backmost retaining member 11c. The
exhaust side rocker shaft 34 (constituted of a hollow member) is
inserted in the respective exhaust rocker shaft retaining holes 20b
so as to allow the shaft 34 to extend from the foremost retaining
member 11a to the backmost retaining member 11c. Likewise, a
support shaft 35 (constituted of a hollow member) is fitted in the
respective attaching seats 21 so as to allow the shaft 35 to extend
from the foremost retaining member 11a to the backmost retaining
member 11c.
Likewise, the camshaft 15 is arranged between the respective
journal bearing surfaces 22 and the journal bearing surfaces 25 so
as to allow the shaft 15 to extend from the foremost retaining
member 11a to the backmost retaining member 11c. A plurality of
journals 37 (shown in FIG. 6) formed on the shaft part of the
camshaft 15 are received between the journal bearing surfaces 22
and the journal bearing surfaces 25, thereby rotatably supporting
the camshaft 15.
Incidentally, each of parts of the camshaft 15 between the
respective journals 37 (between the cylinders) includes a cam group
constituted of an intake cam 38a arranged in the center and (two)
exhaust cams 38b arranged on both sides.
The variable valve operating mechanism 13 (intake side) is attached
to parts of the support shaft and the control shaft between the
above-mentioned holder members 18a, and the rocker arm mechanism 17
(exhaust side) is attached to parts of the exhaust rocker shaft 34
(for each cylinder).
Here, the respective mechanisms will be described below. As shown
in FIGS. 3 and 5, a valve drive mechanism of a type called a swing
cam type in which a swing cam 50 is used, for example, a mechanism
in which a rocker arm 40, a swing cam 50, and a center rocker arm
60 are combined with each other is used as the variable valve
operating mechanism 13.
The above elements will be described below. As the rocker arm 40,
the one having a bifurcate arm shape is used. Specifically, the
rocker arm 40 is provided with a pair of L-shaped rocker arm pieces
43 having needle rollers 41 rotatably provided between one ends of
the pieces 43 and having adjust screw sections 42 serving as valve
drive sections provided at the other ends of the pieces 43.
Further, a part of the control shaft 14 between the holder members
18a is swingably inserted in a pair of support holes 44 formed in
intermediate parts of the respective rocker arm pieces 43. Further,
the needle rollers 41 are arranged on the support shaft 35 side,
and the pair of adjust screw sections 42 are arranged on the
opposite side of the support shaft 35.
As shown in FIGS. 3 and 5, a structure in which a supporting boss
52 having a cylindrical shape is provided at one end of an arm
section 51, a cam surface 53 extending in the vertical direction is
provided at the other end of the arm section 51, and a slide roller
54 is rotatably embedded in the lower part of the arm section 51 in
such a manner that the outer circumferential surface thereof is
exposed from the lower side is used for the swing cam 50.
Incidentally, reference numeral 54a denotes a shaft member for
supporting the slide roller 54. A part of the support shaft 35
between the holder members 18a is swingably fitted in the
supporting boss 52. As a result of this, the cam surface 53 at the
distal end of the arm section 51 is in rolling contact with the
needle rollers 41.
A pusher receiving rib 56 is protruded from an upper part of the
supporting boss 52. A pusher 57 having, for example, a piston
structure is combined with the rib 56 at a lower position of the
rib 56 in an inclined posture. This pusher 57 is supported by
fitting a C-shaped leg section 58 formed on the side part thereof
on a part of the exhaust side rocker shaft 34.
Incidentally, an installation seat 59 is formed at a lower part of
the pusher 57. A structure is made such that when the variable
valve unit 4 is attached to the cylinder head 1 by means of the
installation seat 59, an energizing force is imparted to the swing
cam 50 (this is because when the installation seat 59 is provided
on the cylinder head 1, the pusher is rotationally displaced using
the rocker shaft 34 as a fulcrum).
The center rocker arm 60 is, as shown in FIGS. 3 and 5, constituted
of an L-shaped part arranged at a position surrounded by the intake
cam 38a, slide roller 54, and control shaft 14.
The center rocker arm 60 includes a relaying arm section 61
extending toward the slide roller 54 above, and a fulcrum arm
section 62 extending toward a part immediately below a part of the
control shaft 14 located at a lateral position.
An inclined surface 65 for controlling the movement of the swing
cam 50 is formed on a distal end surface of the relaying arm
section 61. This inclined surface is a flat surface having a lower
part on the control shaft 14 side and a higher part on the rocker
shaft 34 side. Further, a slide roller 63 is supported at an
intermediate part at which both the arm sections 61 and 62
intersect each other so as to be rotatable in the same direction as
the intake cam 38a.
Further, in the relaying arm section 61 interposed between the
intake cam 38a and the swing cam 50, the slide roller 63 is in
rolling contact with the cam surface of the intake cam 38a, and the
inclined surface 65 of the relaying arm section 61 is bumped
against an outer circumferential surface of the slide roller 54 of
the swing cam 50. As a result of this, the displacement of the
intake cam 38 is transmitted to the swing arm 50 through the
relaying arm section 61.
Further, a support pin 66 is flexibly supported on the fulcrum arm
section 62 by means of a pin 67. A distal end of the support pin 66
is rotatably inserted in a through hole 68 formed on the lower side
of the control shaft 14 in a direction perpendicular to the axial
direction, whereby the control shaft 14 is caused to support the
center rocker arm 60.
By virtue of this support, when the control shaft is 14
rotationally moved, the rocker arm 60 that swings around the pin 67
(end of the support pin 6) serving as a fulcrum can move in a
direction intersecting the camshaft 15 (in the lead angle direction
or the lag angle direction) while changing the position at which
the rocker arm 60 is in rolling contact with the center intake cam
38a.
In this movement, the opening/closing timing and the valve lift
amount of the intake valve 8a can be simultaneously and
continuously varied. That is, the upper part of the cam surface 53
is a base circle section (formed by, for example, an arcuate
surface having the axis of the support shaft 35 as a center
thereof), and the lower part of the cam surface 53 is a lift
section (formed by, for example, an arcuate surface having the same
shape as the cam shape of the lift region of the intake cam 38a)
continuing from the base circle section.
When the slide roller 63 of the center rocker arm 60 moves in the
lead angle direction or the lag angle direction of the intake cam
38a, the posture of the swing cam 50 is changed, and the region of
the cam surface 53 in which the needle rollers 41 move is
changed.
In other words, the ratio of the base section to the lift section
in which the needle rollers 41 travel is changed. A change in the
ratio of the base section to the lift section accompanied by a
change in the phase in the lead angle direction and a change in the
phase in the lag angle direction continuously changes the valve
lift amount of the intake valve 8a while largely changing the
opening/closing timing of the intake valve 8a. In this case, the
valve-closed period is more changed than the valve-opened period.
This is output from the rocker arm 40 as the valve drive output. At
this time, in order to prevent the alignment of the slide roller 54
with the inclined surface 65 from being shifted, a pair of guide
walls 51b extending from wall sections 51a sandwiching the slide
roller 54 from both sides (in the width direction) to both sides of
the distal end of the relaying arm section 61 bumping against the
slide roller 54 are formed on the wall sections 51a as shown in
FIGS. 3 and 5.
Specifically, the guide walls 51b are provided in such a manner
that they cover the contact point at which the slide roller 54 of
the swinging swing cam 50 and the inclined surface 65 of the center
rocker arm 60 are in contact with each other. As a result of this,
the center rocker arm 60 is prevented from being shaken around the
support pin 66 serving as a fulcrum. To the part of the control
shaft 14 in which the support pin 66 is inserted, an adjustment
mechanism 70 is attached as shown in FIGS. 3 and 5. In the
adjustment mechanism 70, a structure is employed in which a
threaded hole 71 continuing from the through hole 68 and opening
upwardly is formed at, for example, the part of the control shaft
14, and, for example, a screw member 73 having a slot 72 for
screw-driving at a head part thereof is screwed into the threaded
hole 71 so that it can be advanced or retreated.
In other words, the adjustment mechanism 70 has a structure in
which the protrusion amount of the support pin 66 is changed by a
rotating operation of the screw member 73, whereby the rolling
contact position of the slide roller 63 is changed. Further, a
change in the rolling contact position of the slide roller 63
changes the posture of the center rocker arm 60 and the posture of
the swing cam 50, thereby adjusting the valve opening/closing
timing and the valve lift amount (each of which is a valve
characteristic). The screw member 73 is locked by a locknut 74.
Incidentally, a reference numeral 75 denotes a notch forming a seat
surface of the lock nut 74.
A proximal end part of an arm member 78 extending in the radial
direction of the control shaft 14, i.e., in this case, extending
upwardly is fixed (by a screw) to an end of the control shaft 14
protruding from the foremost holder member 18a by means of, for
example, a screw member 77 as shown in FIGS. 2 and 3. Rotational
movement necessary for continuous control of the valve
characteristic is input from the end of the arm member 78.
In the rocker arm mechanism 17 (exhaust side), a structure is
employed in which a pair of rocker arms 80 are rotatably assembled
on both sides of the leg section 58 of the pusher 57 at a part of
the rocker shaft 34, as shown in FIGS. 3 and 5.
Specifically, each of the rocker arms 80 has a support hole 81 at
an intermediate part thereof, has a roller member 82 serving as a
contact piece at an end thereof, and has an adjusting screw section
83 serving as a valve drive section at the other end thereof.
Then, the part of the rocker shaft 34 between the holder member 18a
and the leg section 58 (pusher 57) is swingably inserted in the
support holes 81 of the rocker arms 80. Each of the roller members
82 is arranged on the exhaust cam 38b side and the adjust screw
section 83 is arranged on the opposite side. That is, each rocker
arm 80 is in a state where it can be combined with the exhaust
valve 9a.
As shown in FIGS. 3, 6, and 7, the fixing bolt member 18c is
inserted from the seat surface 90 formed on the top surface of each
holder member 18a directly above the rocker shaft 34. The fixing
bolt member 18c linearly penetrates (skewers) a central part of the
rocker shaft 34 in the radial direction, a wall part on the support
shaft 35 side (one side of the camshaft 15), the support shaft 35
being adjacent to the camshaft 15, and the cap part of the cap
member 18b on the rocker shaft 34 side.
The fixing bolt 18c is obliquely inserted from each seat surface
21a formed in the upper surface of the support shaft 35 arranged at
the highest position. As a result of this oblique insertion, the
wall part between the rocker shaft 34 and the control shaft 14, the
wall part between the camshaft 15 and the control shaft 14, and the
cap part of the cap member 18b on the control shaft 14 side are
obliquely and linearly penetrated (skewered) by the fixing bolt
18c.
However, reference numerals 92 and 93 denote bolt insertion holes
(only a part of them is shown in FIG. 3), which are formed linearly
or obliquely linearly in the holder member 18a and the cap member
18b. Incidentally, as for the number of the fixing bolt members 18c
to be inserted obliquely, one bolt member 18c is used in the holder
member 18a and the cap member 18b arranged at the foremost part or
the backmost part, and two bolt members 18c are used in the holder
member 18a and the cap member 18b arranged between the cylinders to
which a load heavier than that applied to the member 18a and 18b
arranged at the foremost part or the backmost part is applied
(because a load incidental to the variable valve motion is applied
to the member 18a and 18b from both sides).
Furthermore, the shaft displacement detection sensor 16 for
detecting the rotational displacement of the control shaft 14 is
detachably attached to the sensor attaching boss 31b provided on
the backmost holder member 18a by means of, for example,
screws.
That is, in the variable valve unit 4, the variable valve operating
mechanism 13, the shaft displacement detection sensor 16, the
rocker arm mechanism 17 of the exhaust side, the camshaft 15, and
the adjustment mechanism 70 are modularized into a structure by the
method in which each part is attached to a frame-like structure
having high rigidity constituted of the shafts 14, 34, and 35 and
the retaining members 11a to 11c.
Accordingly, each of the shafts 14, 34, and 35 plays a role of the
frame, and hence the retaining members 11a to 11c can be provided
solely at positions where they are required without increasing the
size, and the weight of the variable valve unit 4 itself can be
minimized.
Further, the shaft displacement detection sensor 16 is positioned
so as to be protruded from the cylinder head 1 and the rocker cover
3 to the outside by appropriately setting in advance the cylinder
part 31a and the sensor attaching boss 31b. Thus, when the variable
valve unit 4 is accommodated in a space between the cylinder head 1
and the rocker cover 3, the entire assembly other than the shaft
displacement detection sensor 16 can be accommodated in the space
between the cylinder head 1 and the rocker cover 3, and only the
shaft displacement detection sensor 16 is exposed to the
outside.
By virtue of such modularization, the variable valve unit 4 becomes
a structure in which cylinder-to-cylinder variation can be adjusted
singly. Thus, in the variable valve unit 4, cylinder-to-cylinder
variation and the sensor output can be adjusted before the
mechanism 4 is attached to the cylinder head 1. As a result, in the
variable valve unit 4, cylinder-to-cylinder variation and the
sensor output is adjusted before the mechanism 4 is attached to the
cylinder head 1, and then the mechanism 4 is attached to the
cylinder head 1 as shown in FIGS. 2 and 7.
This point will be specifically described below. It is recommended
for the variable valve unit 4, modularized before it is attached to
the cylinder head 1, to be subjected to adjustment of
cylinder-to-cylinder variation and the sensor output on a sub-line
separate from the mainline for assembling engines by using a
simulation system in which a cylinder head of an engine is
simulated.
For example, a modularized variable valve unit 4 is attached to a
simulated cylinder head, and a simulated drive apparatus (not
shown) is also attached thereto. It is only required to adjust the
opening/closing timing and the valve lift amount so as to be
uniform and appropriate in the respective cylinders with respect to
the target lift by advancing or retreating the screw member 73 of
the adjustment mechanism 70 of each cylinder, and attaching the
shaft displacement detection sensor 16 so that a signal output
conforming to the target lift can be obtained.
The variable valve unit 4 that has been adjusted is transferred by
using a jig or a transportation apparatus (both are not shown) as
it is so that the adjustment can be maintained so as to be set at a
regular position of an actual cylinder head 1 (assembly of a
cylinder block is already finished) on the main line for assembling
engines, i.e., at module installation seats 94 and 300 (seat
surfaces for receiving the seat surface 27: shown in FIGS. 5 to 7),
for example, already formed on the top surface 1y.
Specifically, both the side parts (including the leg parts 29) of
the cap member 18b are placed on the module installation seats 94
and 300, and the threaded part 18d (formed only at each distal end)
of each of the fixing bolt members 18c on both sides protruding
from parts near both sides of the camshaft 15 is screwed into each
of the threaded holes 18e (shown in only FIG. 7) formed in the
module installation seats 94 and 300.
As a result, the already adjusted variable valve unit 4 is attached
to the top surface 1y of the cylinder head 1 on the main line.
Incidentally, each adjust screw section 42 of the intake side
rocker arm 40 is arranged at a stem end of the intake valve 8a.
Each adjust screw section 83 of the exhaust side rocker arm 80 is
arranged at a stem end of the exhaust valve 9a.
The installation seat 59 bumps against the installation seat 1c
(shown in FIGS. 1 and 5) formed on the inner surface of the
peripheral wall 1a of the cylinder block 1, the entire pusher 57 is
supported by the leg section 58, and the swing cam 50 is energized
in a direction in which a distal end thereof is forced down.
On the other hand, as shown in FIGS. 1 to 3, a driving source
apparatus for driving the variable valve operating mechanism 13,
for example, an electrically-driven actuator unit 95 (corresponding
to an actuator) is installed at the foremost part of the cylinder
head 1.
The electrically-driven actuator unit 95 includes a motor section
96 of a lateral (width direction of the cylinder head 1) type
arranged outside the peripheral wall 1a of the cylinder head 1, a
reduction gear section 97 (for reducing the motor output) connected
to the front part of the motor section 96, and a screw shaft 99
connected to the output section of the reduction gear section 97
through a universal joint 98. These are formed into one part as a
driving unit.
This electrically-driven actuator unit 95 is attached to the
cylinder head 1 in a direction in which the axis thereof intersects
the variable valve unit 4 by fixing the leg section 97b formed on
the casing 97a of the reduction gear section 97 to the top surface
1y of the cylinder head 1 or the rocker cover attaching seat 1b by
means of bolts.
In this way, the motor section 96 is caused to protrude toward the
outside of the cylinder head 1, and the screw shaft 99 is caused to
extend to the arm member 78 end (variable arm mechanism 13) side.
That is, the screw shaft 99 extends to the opposite side of the
motor section 96.
Incidentally, a part of the peripheral wall 1a or the rocker cover
3 at which the electrically-driven actuator unit penetrates the
wall 1a or the cover 3 is formed into a fan-shaped opening.
A nut member 100 is screw-fitted on the screw shaft 99 so that it
can be advanced or retreated. The nut member 100 is constituted of
a pin-shaped member having a flange part 100c at one end thereof,
and having a threaded through hole 100a formed in the axial
direction thereof at an axis part thereof. The thread hole 100a
penetrates the nut member 100 in the diameter direction. The
threaded hole 100a of the nut member is screw-fitted on the screw
shaft 99 so that it can be advanced or retreated. This nut member
100 is attached to the distal end of the arm member 78, and the
control shaft 14 can be driven by the electrically-driven actuator
unit 95.
That is, the nut member 100 is rotatably fitted in a support
cylinder 78a formed at the distal end of the arm member 78
(variable valve unit 4) and, for example, a C-shaped clip member
100b is fitted on the distal end of the nut member 100 so as to
allow it to prevent the nut member 100 from slipping off the
support cylinder 78a, thereby attaching the nut member 100 to the
arm member 78.
The part of the screw shaft on both sides of the nut member 100
penetrates a pair of elongated holes formed on both sides of the
peripheral wall of the support cylinder 78a and extending in the
circumferential direction. When the motor section 96 is operated,
the screw shaft 99 is rotated, and the nut member 100 is moved
along the screw shaft 99 which is swingable. As a result, the arm
member 78 is swung, and the control shaft 14 is rotated. In other
words, by the driving of the electrically-driven actuator unit 95,
the opening/closing timing of the intake valve 8a and the valve
lift amount can be continuously controlled.
As shown in FIG. 2, the rocker cover 3 is formed into a box-like
shape in accordance with the shape of the cylinder head 1. Further,
at parts of the peripheral edge of the rocker cover corresponding
to the penetration position of the shaft displacement detection
sensor 16 and the motor section 96a, fan-shaped notch parts 3a
(only a notch part for the sensor is shown in FIG. 4) for allowing
the shaft displacement detection sensor 16 or the motor section 96a
to penetrate the rocker cover while sealing the penetration parts
are formed.
This rocker cover 3 is set on the rocker cover attaching seat 1b
formed at the peripheral edge of the cylinder head 1 as shown in
FIGS. 1 and 4. As a result, of the units and devices to be mounted
on the cylinder head 1, the shaft displacement detection sensor 16
and the motor section 96 are exposed to the outside of the rocker
cover 3, and the remaining variable valve unit 4, and the greater
part of the electrically-driven actuator unit 95 are accommodated
in the closed space between the cylinder head 1 and the rocker
cover 3.
The shaft displacement detection sensor 16 is exposed to the
outside of the rocker cover 3, and hence the shaft displacement
detection sensor 16 can be replaced from outside while the rocker
cover 3 is closed.
As described above, the variable valve unit 4 becomes a structure
in which cylinder-to-cylinder variation and the sensor output can
be adjusted singly by modularizing the camshaft 15, the shaft
displacement detection sensor 16, and the adjustment mechanism 70.
As a result of this, the cylinder-to-cylinder variation adjustment
and the sensor output adjustment, which require troublesome
operations, can be performed at a place separate from the main line
for assembling engines.
Accordingly, the only work required on the main line for engine
assembly is that for attaching a variable valve unit 4 for which
the cylinder-to-cylinder variation adjustment and the sensor output
adjustment have been finished to a cylinder head 1 on the main
line. The cylinder-to-cylinder variation adjustment work and the
troublesome work for attaching the shaft displacement detection
sensor 16, which are regarded as factors in stagnation, are made
unnecessary.
Therefore, the productivity of engines can be improved. Moreover,
the shaft displacement detection sensor 16 is exposed to the
outside of the rocker cover (FIG. 4), and hence, in a completely
assembled engine or an engine completed as a product, even when
maintenance of the shaft displacement detection sensor 16 is
required, it is easily possible to cope with the requirement.
Particularly, the shaft displacement detection sensor 16 can be
replaced from outside the rocker cover 3, and the replacement work
of the sensor 16 can therefore be easily performed. Even when
replacement of the shaft displacement detection sensor 16 is
required after the engine is completed as a product, it is possible
to quickly cope with the requirement.
Furthermore, the shaft displacement detection sensor 16 for
detecting the rotational displacement is arranged at one end of the
control shaft 14, whereby the rotational displacement can be
directly detected, adjustment accuracy can be enhanced, and
accurate control can be enabled.
The other end of the control shaft 14 is coupled to the
electrically-driven actuator unit 95, whereby even the elastic
torsion of the control shaft 14 caused by valve lift reaction force
can be detected as the rotational displacement, and accurate
control is enabled.
Moreover, in the variable valve unit 4, modularization including
the shaft displacement detection sensor 16 and the arm member 78,
which is an actuator coupling member, is enabled, and hence the
number of assembly man-hours can be reduced.
Furthermore, by employing the structure in which the holder members
18a for holding the one side of the camshaft 15 in the diametric
direction, the variable valve operating mechanism 13, the
adjustment mechanism 70, and the shaft displacement detection
sensor 16, the cap members 18b for holding the remaining one side
of the camshaft 15, and the fixing bolt members 18c penetrating the
holder members 18a and the cap members 18b are combined with each
other as the retaining members 11a to 11c, the fixing bolt members
18c used for attachment to the cylinder head 1 can also be used as
parts for modularization as they are, and the work for
modularization and the adjustment work are performed on the basis
of the fixing bolt members 18c set as the standard, and hence
highly accurate modularization of the variable valve unit 4 and
highly accurate adjustment can be performed.
Next, a valve unit of an internal combustion engine according to a
second embodiment of the present invention will be described below
with reference to FIG. 8. Incidentally, a configuration having the
same function as the first embodiment will be denoted by using the
same reference symbols as those in the first embodiment, and
explanation of them will be omitted.
This embodiment differs from the first embodiment in including a
variable valve operating mechanism 200 in place of the variable
valve operating mechanism 13. The other part of the structure may
be identical to the first embodiment. The point of the second
embodiment different from the first embodiment will be specifically
described below.
FIG. 8 is a cross-sectional view showing an engine 10 of this
embodiment. As shown in FIG. 8, in this embodiment, the engine is
provided with the variable valve operating mechanism 200 in place
of the variable valve operating mechanism 13. The variable valve
operating mechanism 200 has a function of adjusting the
opening/closing operation of an exhaust valve 9a and not that of an
intake valve 8a.
The variable valve operating mechanism 200 has a structure in which
the intake side and the exhaust side are replaced with each other
in the structure of the variable valve operating mechanism 13
described in the first embodiment (accordingly, the configuration
having the same function as the first embodiment is denoted by the
same reference symbols).
In the variable valve operating mechanism 200, the control shaft 14
doubles as a rocker shaft of the exhaust side. Further, on the
intake side, an intake rocker shaft 201 is provided in place of the
control shaft 14.
An intake valve rocker arm (not shown) is attached to the intake
rocker shaft 201. The intake valve rocker arm drives (opens/closes)
the intake valve 8a. A structure for driving the intake valve 8a in
this embodiment may be a mirror image structure of the structure
for driving the exhaust valve 9a in the first embodiment.
Even when the variable valve operating mechanism 200 has a
structure in which driving of the exhaust valve 9a can be adjusted
as in this embodiment, the same advantage as in the first
embodiment can be obtained.
Incidentally, the present invention is not limited to the firs and
second embodiments described above, and may be variously modified
and implemented within the scope not deviating from the gist of the
present invention. For example, the variable valve operating
mechanism of the swing cam type is described as an example in the
first and second embodiments. The present invention is not limited
to this, and a variable valve operating mechanism of another
structure may be used.
Additional advantages and modifications will readily occur to those
skilled in the art. Therefore, the invention in its broader aspects
is not limited to the specific details and representative
embodiments shown and described herein. Accordingly, various
modifications may be made without departing from the spirit or
scope of the general inventive concept as defined by the appended
claims and their equivalents.
* * * * *